We conducted a rigorous monitoring program to develop appropriate conservation plans for swift foxes (Vulpes velox). We set 20 cage traps on 51 grids to estimate rates of occupancy in eastern Colorado. Every 50th grid was selected systematically with a randomly selected starting grid from a list of 2,566 grids ranked by percentage of shortgrass prairie. We trapped 31 August 2004–12 February 2005, with each grid trapped 3 nights. Upon capture, we marked individual foxes with a unique identifier, and determined gender prior to release. We centered a 6.4 by 8.0 km-rectangle over each grid trapped and calculated percentage of shortgrass prairie using a GIS. We caught 136 swift foxes on 40 grids, including 12 recaptures; 71% of captures were in grids with >50% shortgrass prairie. We estimated the proportion of 4.8 by 6.4 km-grids in eastern Colorado occupied by swift foxes to be ψ ˆ  =  0.711 (SE  =  0.069, 95% CI 0.576–0.846), with no evidence of a decline from the 1995–1997 surveys.